In various situations such as vehicle dealerships, vehicle rentals, equipment rentals, vehicle repair shops and the like, numerous keys are being held at any given time. It is important to control access to such keys so that only authorized individuals may remove the keys and also to be able to identify which individual has possession of a particular key at any given time.
A number of systems have been patented in the area of devices for controlling access to stored keys in which a master key is used to release the subject key or article. U.S. Pat. No. 4,472,952 Hollowell, Jr. discloses a system for the management of the issuance and return of articles such as keys, tools and the like. It uses a master unlocking key to engage a geared locking bar which then frees the locking key attached to the article and locks the master key in the device. The master key is released when the locking key is re-inserted into the device and turned to cause a gear to move the geared locking bar to the original position. U.S. Pat. No. 4,641,509 Batchelor et al. discloses a system for retaining and controlling keys in which a universal key turns a lug which engages a notch in the subject key to retain it or release it when the universal key is returned to its original position. In this system the subject keys must be notched by a grinder in order for the system to work. U.S. Pat. No. 5,505,066 Baucom discloses a device for alternately locking a selected one of a pair of keys and releasing the other key for removal from the device. It uses a visitor key having a geared end which engages a geared slider and moves the slider when the visitor key is rotated to alternately release the home key and secure the visitor key or secure the home key and release the visitor key. A system of cams and pins prevents the visitor key from being removed when the home key is removed and vice versa.
U.S. Pat. No. 5,372,021 Smith discloses a key control device which uses a primary key and lock and a secondary key and lock. The cylinders of the two locks are interconnected by a tie rod or gears such that insertion of one of the two keys frees the second key and retains the first key, and vice versa. U.S. Pat. No. 5,878,613 Tabacchi et al. discloses a key control device which uses an access key and lock and a stored key and lock. Rotation of the keys rotate cams which engage with a lid whereby only one key can be removed at any time and removal of one key prevents removal of the other key.